Insulin dependent diabetes mellitus (IDDM) is caused by an autoimmune process which destroys the insulin-producing beta cells. Diabetes becomes clinically evident only after the vast majority of beta cells are irrevocably destroyed (perhaps 90%) and the life of the individual becomes dependent on an exogenous supply of insulin. In other words, at the time of clinical diagnosis, the autoimmune process has already done irreversible damage, most of it without noticeable symptoms.
Successful treatment of the autoimmune process responsible for the disease ideally should be initiated before the patient has overt symptoms of diabetes and requires insulin replacement for his or her own lost capability to produce insulin. Termination of the autoimmune process would result in cure of the disease and prevention of the need for exogenous insulin only if the disease process could be halted while the patient still possessed a sufficient number of beta cells to provide adequate amounts of endogenous insulin. Therefore, any form of therapy would be more effective if persons at risk could be identified while they were yet without overt symptoms of IDDM and before the patients require exogenous insulin. About 90% of new cases of IDDM occur outside of families with known cases. Therefore, assays suitable for mass screening are urgently needed to detect the subclinical disease process at a stage before it is irreversible.
Fortunately, there are a variety of animal models for IDDM, including BB rats and NOD mice (for example, see Rossini et al., Ann. Rev. Immunol., 3:289-320, 1985). Many of the animals develop autoimmune IDDM spontaneously, and demonstrate many of the features of IDDM in humans.
Heat shock proteins (hsp's) are a family of proteins produced by cells exposed to elevated temperatures or other stresses. The hsp's include proteins of various molecular weights, including 20KD, 65-68KD, 70 KD, 90 KD, 110 KD, and others. The heat shock proteins are ubiquitous throughout nature; they are produced by bacteria, yeasts, plants, insects, and higher animals, including humans. The hsp protein molecules are highly conserved and show remarkable homology between all of these diverse creatures. Because of their extreme conservation over evolutionary time, heat shock proteins are thought to perform vital functions. They usually exhibit increased synthesis following exposure of cells to stressful stimuli including heat, certain metals, drugs, or amino acid analogues. Nevertheless, the special functions of these proteins so far are obscure.
For example, patients with systemic lupus erythematosus (SLE) were observed to have antibodies to a 90 KD heat shock protein (Minota et al., J. Clin. Invest., 81:106-109, 1988). The function of these antibodies to hsp90 are not known.
Hsp65 was found to be involved in adjuvant arthritis in rats, cf. van Eden et al., Nature, 331:171-173, 1988. Adjuvant arthritis is an autoimmune arthritis triggered by immunizing certain strains of rats to Mycobacterium tuberculosis (MT) organisms. It was found that the disease could be transferred to immunologically naive, irradiated rats by a clone of T-lymphocytes reactive to a 9 amino acid peptide sequence (180-188) of the hsp65 of MT. Thus, adjuvant arthritis appeared to be an autoimmune disease produced by anti-hsp65 T-lymphocytes. The autoimmune attack against the joints was attributed to partial sequence homology between the 180-185 hsp65 peptide and a segment of the link protein of the cartilage proteoglycan (cf. Cohen, Scientific American, 258:58-60, 1988). It was also found that T-lymphocytes from the synovial fluids of patients with rheumatoid arthritis responded to the hsp65 of MT (cf. Res et al., Lancet, II:478-480, 1988).
Administration of hsp65 to rats before induction of adjuvant arthritis was found to prevent the later development of arthritis. Thus, the presence of an immune response to hsp65 was associated with arthritis in both rats and humans, and administration of hsp65 could lead to resistance to arthritis.
European patent application 262,710 discloses polypeptides useful for alleviation, treatment, and diagnosis of autoimmune arthritis and similar autoimmune diseases.
The complete primary structure, including nucleotide and deduced amino acid sequence of the human P1 protein has recently been published in Jindal, S. et al, "Primary Structure of a Human Mitochondrial Protein Homologous to the Bacterial and Plant Chaperonins and to the 65-Kilodalton Mycobacterial Antigen," Molecular and Cellular Biology, 9, 5, 2279-2283, 1989. This protein, disclosed as having a molecular weight of about 63 kDa, is the human heat shock protein referred to herein as the hHSP65 protein. The entire contents of this publication are hereby incorporated herein by reference.